If you're having issues installing Visual Studio 2008 RTM and had installed Visual Studio 2008 RC or if you want to remove it.  You might want to consider using the following tool, which cleanly removes Visual Studio 2008 RC or RTM.

http://msdn2.microsoft.com/en-us/vs2008/bb968856.aspx

NOTE: this tool does not remove .NET Framework 3.5.  You should use the following .NET Framework uninstall tool to do so.

http://blogs.msdn.com/astebner/archive/2007/12/04/6659905.aspx